The present invention relates to a multiblade impeller and, more particularly, to a multiblade impeller suitable for industrial machinery, air conditioning equipment, and the like.
Conventionally, a multiblade impeller comprising a main plate, a side plate and a plurality of blades generally has a fixing structure for fixing the blades to the main plate and side plate, in which projecting pieces provided at end portions of the blade are inserted in blade mounting holes provided in flat portions of the main plate and side plate, and the projecting pieces are bent to fix the blade to the main plate and side plate so as to press the main plate and side plate down.
Regarding the fixing structure for fixing the blades to the main plate and side plate, the conventional multiblade impellers have been disclosed, for example, in JP-A-60-93200, JP-A-8-319992 and JP-A-7-127598.
In the multiblade impeller disclosed in JP-A-60-93200, a blade fixing insertion piece is provided in a joint portion between a blade and a side plate having a blade mounting hole, and the insertion piece is deformed to pressingly fix the blade and the side plate.
In the multiblade impeller disclosed in JP-A-8-319992, a plastic or brazing metal is filled in joint portions between a main plate/side plate and a blade to fix the blade to the main plate and the side plate.
In the multiblade impeller disclosed in JP-A-7-127598, protrusions are provided on side surfaces of a blade, and the protrusions are closely fitted in fitting grooves in a main plate and a side plate to fix the blade to the main plate and the side plate.
In the general fixing structure of the above-described conventional multiblade impeller, when the main plate, side plate and blades are thin, a high fixing strength cannot be obtained, and hence sufficient reliability cannot be attained. Therefore, there is need to increase their thickness, which leads to an increase in cost.
Also, since the main plate, the side plate and the blades are of a simple plate shape, a rigidity necessary for an impeller cannot be obtained unless the thicknesses thereof are increased. As a result thereof, there is a problem that the weight of the multiblade impeller increases to affect performance of products in which such multiblade impellers are used. In other words, since the multiblade impeller generally repeats start and stop, it is desired to facilitate the start and stop of the multiblade impeller and hence to improve the performance of the product in which the multiblade impeller is used by decreasing the weight of the multiblade impeller, and further it is desired to improve the reliability of the product in which the multiblade impeller is used by decreasing a load to be applied to driving system of the multiblade impeller. In particular, in recent years, since the rotational speed control of the multiblade impeller has been implemented by an inverter, it is desired to improve the response of rotational speed control and hence to improve the performance of the product in which the multiblade impeller is used by decreasing the weight of the multiblade impeller.
In the above-described multiblade impeller disclosed in JP-A-60-93200, because of the fixing structure in which the blade fixing insertion piece is provided in the joint portion between the blade and the side plate having the blade mounting hole, and the insertion piece is deformed to press the blade and the side plate, the blade fixing insertion piece is needed, and also troublesome work for deforming the blade fixing insertion piece along the blade is necessary, which results in an increase in cost. In the multiblade impeller disclosed in JP-A-60-93200 as well, since the main plate, the side plate and the blades are of a simple plate shape, rigidity necessary for an impeller cannot be obtained unless the thicknesses thereof are increased, so that the multiblade impeller disclosed in JP-A-60-93200 has a problem similar to that of the above-described general fixing structure.
In the above-described multiblade impeller disclosed in JP-A-8-319992, because of the fixing structure in which plastic or brazing metal is filled in the joint portions between the main plate/side plate and the blade to fix the blade to the main plate and the side plate, the brazing material is needed, and also troublesome work for filling the brazing material in the joint portions is necessary, which results in an increase in cost. In the multiblade impeller disclosed in JP-A-8-319992 as well, since the main plate, the side plate and the blades are of a simple plate shape, rigidity necessary for an impeller cannot be obtained unless the thicknesses thereof are increased, so that the multiblade impeller disclosed in JP-A-8-319992 has a problem similar to that of the above-described general fixing structure.
In the above-described multiblade impeller disclosed in JP-A-7-127598, although the blade can be closely fitted in the fitting grooves in the main plate and the side plate by the protrusions provided on the side surfaces of the blade, the main plate, the side plate and the blades are substantially of a simple plate shape. Therefore, rigidity necessary for an impeller cannot be obtained unless the thicknesses of the main plate, the side plate and the blades are increased, so that the multiblade impeller disclosed in JP-A-7-127598 has a problem similar to that of the above-described general fixing structure.